1. Field of the Invention
The present invention relates generally to the technology of operating gasiform substance in the vacuum or low-pressure environment, and more particularly, to a device for operating gas in the vacuum or low-pressure environment and for observation of the operation.
2. Description of the Related Art
As far as the technology of microscopic observation is concerned, it is known that a user can employ an electron microscope with its high-power magnification to do scientific research of nanometer substances.
A conventional electron microscope works by utilizing an electron beam to probe the substance. It is necessary to utilize the accelerated electron beam by high voltage and to focus the electron beam by using the electromagnetic lenses to do the microscopic observation in a vacuum environment. As shown in FIG. 11, an electron microscope 61 includes a vacuum specimen chamber 62 for receiving a specimen, and an upper pole piece 66 and a lower pole piece 66 both located in the specimen chamber 62 for ensuring precise focus of the electron beam. The distance between the two pole pieces 66 is usually not larger than 1 cm. However, any specimen received in the specimen chamber 62 must be a solid, not a fluid such as liquid or gas, to allow observation in such vacuum environment, since a fluid specimen is subject to immediate boiling, volatilization, or the like.
To overcome the above problem and to allow the specimen received in the electron microscope to coexist with a specific gas, an environment chamber for controlling vapor was invented in 1976 (Hui S. W. et al., Journal of Physics E 9, 69, 1976). The modified electron microscope 71, as shown in FIGS. 12 and 13, includes a heightened specimen chamber 72, a water tank 74 mounted inside the specimen chamber 72, and an environment chamber 76. The environment chamber 76 has two spacers 762 partitioning its center off into a vapor layer 764 and two buffer layers 766 located respectively below and above the vapor layer 764. The water tank 74 has a temperature-controllable vent pipe 741 connected with the vapor layer 764 for offering vapor of the same temperature as that of the environment chamber 76 to avoid condensation resulting from the entry of the vapor into the vapor layer 764. The two spacers 762 and top and bottom sidewalls of the environment chamber 76 are parallel to one another, each having an aperture 763. The apertures 763 are coaxial with one another for penetration of the electron beam. The environment chamber 76 further has a specimen tube 767 extending outwards from the vapor layer 764, a specimen holder 768 extending through the specimen tube 767 into the vapor layer 764 from outside, and an O-ring 769 sealing space between the specimen holder 768 and the vapor layer 764 for insulation between the vapor layer 764 and the outside.
During operation of the electron microscope 71, the vapor inside the water tank 74 keeps flowing into the vapor layer 764. In the meantime, the two buffer layers 766 are evacuated to pump out the vapor leaking from the vapor layer 764, preventing the vapor from flowing out of the two buffer layers 766 through the two apertures 763 of the environment chamber 76. Thus, the gas pressure inside the vapor layer 764 of the environment chamber 76 can be maintained at 50 torrs or so.
Although the aforementioned prior art can enable generation of extremely low-pressure vapor in the vapor layer, there are still some drawbacks for improvement.
1. It is necessary to alter the original design of the electron microscope. However, disassembling and assembling the electron microscope is very complicated, requiring experts to do it well, and is very costly and subject to damage to electron microscope. Thus, such invention still cannot be applied to mass production.
2. Heightening the specimen chamber of the electron microscope may result in alteration of the focal length of the electron beam to further cause aberration and loss of resolution.
3. Increasing the gas pressure inside the vapor layer will result in leakage of the gas into the vacuum zone, as shown in FIG. 13, disabling the operation of standard atmospheric pressure inside the vapor layer. Although dramatically enhancing evacuation for the buffer layers 766 can overcome this problem, the high-speed pumping rate caused by the enhanced evacuation may result in strong turbulence, causing multiple scattering caused by the electrons impinging the gas molecules and further disabling successful imaging of the electron beam or experiment of electron diffraction.
Another research group for modification of the electron microscope presented an experiment of observation of gasiform and solid chemical reactions under the electron microscope in 2002 (Gai P. L., Microscopy & Microanalysis 8, 21, 2002). Such design is similar to the aforementioned invention, but has the following drawbacks. Because the space between the pole pieces inside the electron microscope is about 1 cm high in size and treated as a gas chamber, if the gas pressure inside the environment chamber keeps increasing, the multiple scattering of the electrons will become excessive. As far as this design of the environment chamber of 1 cm in height is concerned, while the gas pressure inside the environment chamber reaches the standard atmospheric pressure, the multiple scattering of the electrons can disable successful imaging of the electron beam or experiment of electron diffraction.
In addition, Gai's design concept is identical to Hui's in that it is necessary to disassemble the primary part of the electron microscope before installing the whole system including the gas chamber and the buffer layers, such that it hardly possible to mass-produce the system.
There were also some similar designs/experiments, such as Lee T. C. (Lee T. C. et al., Rev. Sci. Instrum. 62, 1438, 1991), Robertson I. M. (Robertson I. M. at al., Microscopy Research & Technique 42, 260, 1998), Sharman R. (Sharman R., Microscopy & Microanalysis 7, 494, 2001), etc. However, they all exhibit the same problem of multiple scattering of the electrons while operating the gas chamber at the standard atmospheric pressure.